U.S. Coast Guard begins testing synthetic aids, virtual buoys

Jul 31, 2014 01:26 PM
The Coast Guard is experimenting with synthetic AIS aids to navigation on the approach to San Francisco Bay.

(Courtesy U.S. Coast Guard)

The Coast Guard is experimenting with synthetic AIS aids to navigation on the approach to San Francisco Bay.

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The U.S. Coast Guard has begun to test automatic identification system (AIS) aids to navigation, including virtual buoys, on the West Coast as the first step toward introducing them around the country.

The pilot project, while promising many benefits to mariners, is raising some concerns about whether the training of pilots and watchstanders will be sufficient to handle the new technology. And there are questions about whether the system will be secure from hackers.

AIS is the internationally adopted radio communication system that allows autonomous and continuous exchange of navigation-safety messages between vessels, aircraft, shore stations and aids to navigation (ATON). AIS ATON stations broadcast their identity with a nine-digit Maritime Mobile Service Identity (MMSI) number, position and status at least every three minutes. Broadcasts can originate from an AIS station located on an existing physical aid (Real AIS ATON) or from another location (AIS Base Station).

When an AIS Base Station signal is broadcast to coincide with an existing physical aid it is known as a Synthetic AIS ATON. When a signal is broadcast to a location in a waterway where there is no physical aid, it is known as a Virtual AIS ATON.

All three variations can be received by any existing AIS mobile device, but they require an external system such as AIS message 21-capable ECDIS, ECS, radar or a PC.

Lt. Dave Lewald, of the Coast Guard’s Visual Aids to Navigation branch in the Office of Navigation Systems, noted that AIS has been in use for more than a decade.

“It was initially started as a ship-to-ship collision-avoidance tool,” he said. “But the International Maritime Organization, recognizing that it had capabilities to serve as an aid to navigation, approved it for that use.” This summer, at its next meeting, IMO is expected to approve a set of symbologies.

“Parallel to all of this, the Coast Guard has been erecting what we call the nationwide AIS (NAIS),” Lewald said. The agency can program into the system the ability to transmit two types of AIS ATONs. With a synthetic, “we put that mark out there so when a pilot is coming in they will see the buoy, but on top of that they will have the AIS symbol. It seems kind of redundant, but what that does for us is it allows a quick comparison to make sure that that buoy is still on station. Particularly in a year like this when we had a lot of ice, that’s very important because the buoys kind of moved around quite a bit.”

The Coast Guard established several of these aids near San Francisco in February. The First Coast Guard District in the Northeast is preparing a list of buoys it wants AIS synthetics for as well, he said. And eventually it will be all over the country.

“The second type of AIS ATON that we’re using is literally a virtual in that we broadcast a signal out to an empty spot in the water so the only way you can see it is through your AIS in your radar or if you have an electronic charting system that speaks to your radar,” Lewald said.

The first full-functioning virtual aids were turned on March 12. “We’re using them to mark the call-in points for the San Francisco Traffic Separation Scheme,” he said. “So rather than putting an $85,000 buoy out there just to remind mariners to call in the VTS, we have the synthetics. The only mariners who are required to call in are SOLAS class, so they already have all of this equipment. So this is a phenomenally efficient use.”

“On the Western rivers, we have a real problem with bridges being hit by barge tows,” he said. “So we will be establishing virtuals marking the bridge piers.” Pilots and captains will be able to use the virtual markers to measure the distance between piers.

“What we’re doing is asking commercial users that have the capability to see these things — mostly pilots — and we want to start learning how to use them: what’s the best way to use this available tool that we have,” he said. Mariners with feedback should go to www.navcen.uscg.gov.

The length of the testing is open-ended, Lewald said. It will depend on the feedback from pilots, captains, chart manufacturers and other interested parties.

The feedback has already started.

Capt. Richard Madden, a maritime consultant who holds a Coast Guard unlimited master’s license and master of towing vessels license, said AIS “has proven to be a valuable and versatile method of transmitting information in a relatively small geographic area. While VHF range is normally line-of-sight, or in a best-case scenario 25 to 30 nm, it is not uncommon to see AIS signals picked up over a couple of hundred miles away.”

First seen overseas, he said AIS transmitters are finding their way into lighthouses, port control offices and most recently buoys.

Madden said Real AIS ATONs “is probably the best use of the AIS technology with buoys, as it marries the virtual position transmitted with the actual physical location of the buoy.”

He said a benefit of Synthetic AIS ATONs “might be decreased costs and maintenance, as potentially expensive and sensitive equipment wouldn’t be exposed to the elements. The drawback that jumps to mind is the possibility of the buoy being off station, which would not be reflected by the AIS signature, as the two are not physically connected.”

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